Following the abuse a summer’s worth of sun can deliver to the skin, now is a good time to review the features of a common skin condition related to ultraviolet exposure, actinic keratosis (AK). This is particularly important since AKs are considered to be pre-cancerous with a certain percentage of them advancing into squamous cell skin cancer.
What is an AK? Actinic keratosis, also known as solar keratosis, is a skin lesion that develops on sun-exposed areas of the body such as the face, arms, backs of hands, and lips. They are often rough in texture, resembling warts, and may be felt before actual changes of the skin are noted. Their color can range from flesh-toned to brown or red. Most are small, less than a half inch across. Up to 10% of AKs will advance to become squamous cell skin cancer. Most AKs cause no symptoms, but itching or burning at the site of the skin lesion may be reported.
Who gets AKs? The most current estimate is that up to 58 million Americans have AKs. Most of these people are over the age of 40, since AKs tend to develop slowly following years of sun exposure. They are seen more often in people with fair skin and lighter hair color, but anyone who has had significant sun exposure can get them. AKs also occur more commonly in people with an impaired immune system, such as someone who has had an organ transplant or is on medications to suppress the immune system. The recent trend to use sun lamps or tanning booths has contributed to an increase in the number of AKs that occur each year.
How are AKs diagnosed? Experienced examiners can often make the diagnosis by just looking at the skin lesion. In some cases, a skin biopsy may be necessary to distinguish an AK from skin cancer.
How are AKs treated? Once skin lesions are confirmed to be AKs, it is best to have them removed since it is impossible to know which ones could become cancerous. The following are some of the most commonly used methods for AK removal:
- Topical Medications. These include the FDA-approved medications, 5-fluorouracil (brand name Efudex, others), Imiquimod (brand name Aldara), and a newer medication Ingenol mebutate (brand name Picato). 5-FU ointment or liquid is the most widely used topical medicine for AKs and is effective for visible AKs as well as for those that are not yet apparent. Imiquimod 5% cream works by stimulating the immune system to destroy the lesions. Ingenol mebutate is a gel that is applied for only 2 or 3 days, depending on the concentration of the gel and the location on the body being treated.
- Destructive methods. These include freezing (cryotherapy), scraping (curettage), and burning (cautery). When freezing AKs, a cold substance, such as liquid nitrogen, is applied to the skin lesion. This kills the cells of the AK (along with some normal tissue). As the skin heals, the AK typically does not come back. Curretage requires the use of local anesthesia to numb the skin before using sharp instrument called curettes to scoop out the AK. It is usually done in conjunction with electrodessication, a procedure involving electrical current to kill any remaining AK cells. This last step is similar to cautery which uses electricity to “burn” away AKs.
- Photodynamic therapy involves applying a solution (5-aminolevulinic acid) to the skin that makes it more sensitive to light. Following this, a light source (typically a type of laser) is used to activate the medication that then selectively destroys the AKs. Following healing, new healthy skin appears.
- Chemical peeling is perhaps best known as a treatment for facial wrinkles or other signs of aging. In this procedure a chemical, such as tricholoracetic acid, is applied to the skin with resulting sloughing of the top layer of skin, along with the AKs.
Can AKs be prevented? Since the damage delivered through UV rays from the sun is cumulative, the development of AKs may be inevitable. Nevertheless, here are some of the ways to help prevent AKs from developing:
- Avoid being in the sun during the peak hours for UV exposure between 10 AM and 4PM. Don’t forget that snow and water can concentrate the sun’s rays and increase the risk of burning.
- If sun exposure is unavoidable, use a broad spectrum sunscreen that is effective against UVA and UVB radiation with a SPF of 30 or higher.
- For extra protection wear long sleeves and long pants and a wide-brimmed hat.
- Avoid tanning beds or lights. Despite claims of tanning bed companies and booths, the radiation (predominantly UVA) in the lights that they use increase your risk of developing AKs and skin cancer.
In order to detect AKs or skin cancer in their earliest stages, check your skin regularly and let your doctor know if you notice any suspicious lesions. Look particularly for changes in existing moles or for the development of new skin growths.